JPH02206583A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve a background color and color forming properties by a method wherein an optical recording medium is formed by providing a light absorbing layer containing a specific thiourea derivative and a near infrared absorber and a thermal color-forming layer containing a basic colorless dye and an organic color developer on a substrate. CONSTITUTION:A light absorbing layer containing a near infrared absorber is formed on a substrate. The light absorbing layer is formed by mixing and thermally treating a thiourea derivative shown by a formula I (R1, R2, and R3 represent H, alkyl, alkenyl, aryl, or others) and a metallic compound shown by a formula II (R represents H, alkyl, and others, X represents -COO, -SO4, -SO3, -SO4, and others, and M represents a metal having an atomic weight of 40 or more other than group IA and IIA metal in the periodic table). Furthermore, a thermal color-forming layer containing a basic colorless dye and an organic color developer is laminated thereon to form an optical recording medium. As the metals forming the metallic compound, copper and/or lead are preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording medium that performs recording by irradiating light in the near-infrared region.

(Prior art) The thermal recording method is a direct recording method that does not require development or fixing.
Due to its excellent operability and maintainability, it is widely used in facsimile machines and printers.

However, because the thermal head and heat-generating IC pen are brought into direct contact with the thermal recording paper to perform heating recording, colored melt adheres to the thermal head and heat-generating IC pen, causing problems such as adhesion of scum and sticking, resulting in recording failure. There were also problems with the recording quality.

Particularly in the case of continuous line drawing in the recording flow direction, such as with a plotter printer, it has been impossible to perform continuous printing without causing problems such as adhesion of residue.

Further, it is said that it is difficult to achieve an image resolution of 8 lines/■ or more using a thermal head.

Therefore, a non-contact recording method using light has been proposed as a method of eliminating problems such as adhesion of residue and sticking and further improving resolution.

JP-A-58-209594 discloses an optical recording medium in which at least one set of a near-infrared absorber having an absorption wavelength in the near-infrared region of 0.8 to 2 μl and a thermosensitive coloring material are laminated on a substrate. 1985-94494 discloses the use of one or more heat-sensitive materials and one or more near-infrared absorbers consisting of a compound having a maximum absorption wavelength in near-infrared light of 0.7 to 3 μm. A recording medium is disclosed in which a base material is coated with.

In these publications, the methods of coating the near-infrared absorber and the heat-sensitive coloring material on the substrate or base material include mixing the near-infrared absorber and the heat-sensitive coloring material and coating them, or using a heat-sensitive coloring method. It is disclosed that a material layer is first coated on a substrate or base material, and a near-infrared absorber is applied on the heat-sensitive coloring material layer for lamination or coating.

The near-infrared absorbers disclosed in these publications are dyes such as cyanine dyes, thiol nickel complexes, and squarylium.

In addition to this, near-infrared absorbers include "near-infrared absorbing dyes"
(Kagaku Kogyo 43, May 1986), nitroso compounds and their metal complexes, polymethine dyes (cyanine dyes), complexes of thiol with cobalt and palladium, phthalocyanine dyes, triallylmethane dyes. , immonium, diimmonium dyes, naphthoquinone dyes, and the like are known.

(Problem to be Solved by the Invention) When coating these conventional near-infrared absorbers and heat-sensitive coloring materials on a substrate or base material, as disclosed in the above publication, if they are mixed and coated, , desensitization development is observed, resulting in a decrease in coloring performance, and if a heat-sensitive coloring material layer is first coated on a substrate or base material, and a near-infrared absorber is coated on this material layer, the background color decreases. There is a problem. Furthermore, all of the conventional near-infrared absorbers mentioned above have relatively strong and broad absorption in the visible region and are strongly colored, making it difficult to obtain an optical recording medium with a white ground color, making it difficult to put optical recording materials into practical use. It was an obstacle in doing so.

Therefore, an object of the present invention is to provide an optical recording medium with improved background color and color development.

(Means for solving problems) The above problem is to apply the general formula (I) on the base material, R2-NR.

(In the formula, R,,R2,R, is a monovalent group selected from the group consisting of hydrogen, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, and a 5- or 6-membered heterocyclic residue. and R1 and R2 or R2 and R3 may be linked to form a ring.Multigroups include amino groups, alkyl groups, alkenyl groups, aryl groups, aralkyl groups, nitro groups, halogen groups, hydroxyl groups, alkoxy group, acyl group 1
It may have more than one species as a substituent. ) (hereinafter referred to as the thiourea derivative of the present invention) and the general formula (n) (R-X). M (II) (wherein,
R represents hydrogen, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, and a heterocyclic residue (the polygroup may have one or more substituents), and X represents -coo, -
so,,-3(h.

PO4, O, n is an integer from 1 to 4) or chlorophyll M, M chlorophyllin sodium, bisacetylacetonato M (M is a metal with an atomic weight of 40 or more excluding Group IA and Group IA of the periodic table) Laminating a light absorption layer containing a near-infrared absorber obtained by mixing and heat-treating a metal compound (hereinafter referred to as the metal compound of the present invention) and a heat-sensitive coloring layer containing a basic colorless dye and an organic color developer. achieved by.

In particular, the under layer is a light absorbing layer containing a near-infrared absorber made by heat treating a compound and/or a lead compound and a thiourea derivative, and a heat-sensitive layer containing a basic colorless dye and an organic color developer thereon. The effect is maximized by laminating coloring layers.

Furthermore, by providing a transparent protective layer on the heat-sensitive coloring layer and containing a small amount of a conventionally known near-infrared absorbing dye in, on, or below the protective layer or underlayer, it is possible to A more excellent optical recording medium can be obtained by incorporating a synthetic resin pigment with high near-infrared reflecting ability into the absorption layer.

The present invention is characterized in that, in an optical recording medium comprising a light absorption layer and a thermosensitive coloring layer, the thiourea derivative of the present invention and the metal compound of the present invention are mixed and heat-treated as a light absorbent to be contained in the light absorption layer. The purpose of this invention is to use the heat-treated product as a near-infrared absorber.

This heat-treated product has relatively uniform and strong absorption over the entire near-infrared region of 0.8 to 2.8 μm, has relatively small absorption in the visible region, and It is a near-infrared absorbent suitable for the present invention because it has the property of quickly and efficiently converting into heat and radiating heat.

The near-infrared absorber of the present invention can be obtained from Japanese Patent Application No. 145262/1983 concerning a near-infrared absorbing material made from a thiourea derivative and a copper or lead compound, which the present inventors previously filed. It can be obtained by a method similar to that described in No. 63-232075. That is, the near-infrared absorber used in the present invention is obtained by mixing and heat-treating a thiourea derivative and a metal compound, but the mixing heat treatment refers to immediately mixing the thiourea derivative and the metal compound of the present invention and heating them. There are cases where both are mixed in a dispersion medium and then heated, each is dispersed separately in a solvent and then mixed and heated, or the dispersion medium is removed by drying etc. and then heated. and heating may be performed at the same time.

Other substances that do not impair near-infrared absorption, such as a binder, a dispersant, and a dispersion medium may be added to the mixture as necessary.

The heat treatment method for developing near-infrared absorbency is 2.
There is no particular restriction as long as it can add thermal energy that will cause the components to react and obtain near-infrared absorbing ability, such as electric heaters, induction heating, melt molding of films, thermal heads, semiconductor lasers, and infrared lamps. Can be done.

The heating operation may be carried out in any atmosphere such as the air or an inert gas atmosphere, but is usually carried out in the air.

The heating temperature is generally in the range of 40 to 400°C, preferably in the range of 50 to 350°C.

The heating time is generally in the range of several milliseconds to several tens of minutes. In addition, it is a preferable method to add stirring, rotation, and vibration to increase the frequency of contact between the substances, to uniformly transfer thermal energy, to speed up the reaction, and to homogenize the mixing state.

The blending ratio of the thiourea derivative of the present invention and the metal compound varies depending on the type of both, but generally the thiourea compound is in the range of 0.01 part to 50 parts, preferably 0.1 part to 50 parts, per part of the compound. The range is 10 parts.

Specific compounds of the thiourea derivative of general formula (1), which is one of the constituent components of the near-infrared absorber of the present invention, include 1,3-diphenylthiourea, 1-3-dibenzylthiourea,
1,3-dilaurylthiourea, 1,3-diethylthiourea, 1,3-dimethachlorothiourea, 1-(2-
Including thiazolyl-3-phenylthiourea and 1-benzyl-3-morpholinothiourea, patent application 1986-1
Each compound described in No. 45262 may be mentioned.

Further, specific examples of the metal compound which is the other component of the near-infrared absorber of the present invention include Y and Ti.

Zr, V, Nb, Mn, Fe, Co, Ni, Pd.

These are salts, alkoxides, and hydroxides of organic acids such as Cu, Ag, Zn, Sn, and Pb.

Examples of organic acids include, but are not limited to, those listed below.

Stearic acid, palmitic acid, oleic acid, behenic acid, lauric acid, capric acid, caproic acid, valeric acid, isobutyric acid, butyric acid, propionic acid, acetic acid, formic acid, benzoic acid, orthotoluic acid, metatoluic acid, paratoluic acid, paratertiary acid Butylbenzoic acid, orthochlorobenzoic acid, methachlorobenzoic acid, parachlorobenzoic acid, dichlorobenzoic acid, trichlorobenzoic acid, p-bromobenzoic acid, p-iodobenzoic acid, p-phenylbenzoic acid, 0-benzoylbenzoic acid, p- Nitrobenzoic acid, anthranilic acid, p-
Aminobenzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, phthalic acid, monoester phthalic acid, naphthenic acid, naphthalic acid, tartaric acid, diphenylamine. 2-carboxylic acid, 4-cyclohexylbutyric acid, diethyldithiocarbamic acid, gluconic acid, octylic acid, alkylbenzenesulfonic acid, p-)luenesulfonic acid, naphthalenesulfonic acid, naphthylliaminesulfonic acid, n-dodecylbenzenesulfonic acid, dodecyl sulfuric acid , 2,5-dimethylbenzenesulfonic acid, 2-carbomethoxy-5-methylbenzenesulfonic acid, α-naphthyl phosphoric acid, stearic acid, lauryl phosphoric acid, di-2-ethylhexyl phosphoric acid, isodecyl phosphoric acid.

Examples of the alcohol include alcohols corresponding to the above-mentioned organic acids.

Among these metal compounds, V, Ni, and Co.

Metal compounds of Fe, Ag, Cu, and Pb are preferable as near-infrared absorbers because they have uniform and strong absorption throughout the near-infrared region. Among these, near-infrared absorbers using copper compounds or lead compounds are particularly preferred since they can provide a white background color when used as a light absorption layer.

The degree of near-infrared absorption can be arbitrarily adjusted by adjusting the type and ratio of the thiourea derivative of the present invention and the metal compound, heating temperature, heating time, etc.

The near-infrared absorbent of the present invention obtained in this way has a small absorption in the visible region, but as a result, the absorption in the near-infrared region of 1μ or less is weaker than in other regions, and this tendency The smaller the amount of the near-infrared absorber of the present invention used, the more noticeable it becomes. On the other hand, conventionally known near-infrared absorbing dyes generally have a diameter of 1 μm.
Most of them have absorption peaks below. Therefore, by using the near-infrared absorbing agent of the present invention together with a known near-infrared absorbing dye and adjusting the amount used, a wide range of near-infrared light can be uniformly absorbed and functionally balanced. A light absorbing layer can be formed.

The near-infrared absorber thus obtained is mixed and dispersed with the material constituting the light-absorbing layer, and the light-absorbing layer is formed by spraying, coating, or printing onto a support.

Alternatively, the thiourea compound and the metal compound of the present invention are separately dispersed together with the material constituting the light absorption layer to form a slurry, and this slurry is mixed and sprayed, coated or printed on a support, dried and dispersed. After the medium is removed, heat treatment may be performed to create the near-infrared absorber and the light absorption layer at the same time.

There are no restrictions on the material of the base material, but paper, synthetic paper, and plastic film are common.

The materials constituting the light absorption layer are auxiliary agents such as a binder, a white pigment, and a near-infrared absorption dye.

As the binder, one or more binders are selected and used from among those conventionally used in the heat-sensitive coloring layer described below.

White pigments are not only effective in hiding the coloring of the near-infrared absorber and making the entire optical recording medium appear white, but also in scattering the incident near-infrared light to the surroundings, thereby reducing the scattered near-infrared light. Increases the probability that external light will enter the near-infrared absorber, increasing heat generation efficiency.

Although white pigments strongly reflect visible light on average, they usually reflect near-infrared rays as well as visible light. clay,
Heavy calcium carbonate, precipitated calcium carbonate, titanium oxide, calcium sulfate, barium sulfate, zinc sulfate, satin white, talc, basic magnesium carbonate, zinc oxide, alumina, white carbon, silica gel, colloidal silica, plastic picment, etc. Available are silica gel, colloidal silica, ultradifferential alumina,
It is preferable to use a material that is porous or has a large specific surface area, such as a plastic pigment.

In particular, hollow plastic pigments not only have excellent near-infrared reflectivity (but also have good heat insulation properties, making it difficult for near-infrared absorbers to diffuse the heat generated by absorbing near-infrared light). This is preferable because of the

The near-infrared absorbing dye that supplements the effect of the near-infrared absorber of the present invention generally dissolves relatively easily in a solvent such as water, alcohol, or toluene, and desirably has a solubility of 5% or more. . Specific dyes include polymethine dyes (cyanine dyes), azulenium dyes, pyrylium dyes, and mercaptophenol dyes. It is described as a soluble near-infrared absorber in Japanese Patent Application No. 63-272702 filed as .

This near-infrared absorbing dye can be contained in or between layers of the light absorbing layer and/or protective layer other than the thermosensitive color forming layer of the optical recording medium.

The light-absorbing layer obtained in this manner is laminated with a thermosensitive coloring layer consisting of a basic colorless dye, an organic color developer, a binder, and if necessary quality control agents such as a sensitizer and a filler, to form an optical recording material. get.

The heat-sensitive coloring layer is exactly the same as the coloring layer of heat-sensitive recording paper, which contains a known electron-donating colorless dye and an electron-accepting organic color developer as color-forming components, and is completely different from all the known coloring layers of heat-sensitive recording paper. technology can be applied.

Basic colorless dyes include triphenylmethane-based leuco dyes such as crystal violet lactone, fluoran-based leuco dyes such as 3-diethylamino-6-methyl-7-anilinofluorane, and 3-(4-diethylamino-2-ethoxyphenyl). -Azaphthalide leuco dyes such as -3(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3.6.6'-tris(dimethylamino)spiro[fluorein-9,3'-phthalide ] and other fluorine-based leuco dyes.

In addition, organic color developers include bisphenol A, 4-hydroxybenzoic acid esters, 4-hydroxyphthalic acid diesters, phthalic acid monoesters, bis-(hydroxyphenyl) sulfides, and 4-hydroxyphenylaryl sulfone. 4-hydroxyphenylaryl sulfonates, 1,3-di[2-(hydroxyphenyl)-2-probylcobenzenes, 4-hydroxybenzoyloxybenzoic acid esters, bisphenol sulfones, and the like.

Examples of the binder include fully saponified polyvinyl alcohol having a degree of polymerization of 200 to 1900, modified polyvinyl alcohol such as amide-modified polyvinyl alcohol, hydroxyethyl cellulose, styrene-butadiene copolymer, and the like.

In addition, fatty acid amide, montan wax, etc. are usually used as sensitizers or quality control agents, and fillers such as clay, calcium carbonate or plastic pigments, which are commonly used in the field of paper processing, can be added. In particular, hollow plastic pigments are preferred because they have good near-infrared light reflection and good heat retention.

The materials used in these heat-sensitive coloring layers include basic colorless dyes, organic color developers, binders, sensitizers, Fillers and quality control agents can equally be used in the present invention.

The types and amounts of the organic color developer, basic colorless dye, binder, sensitizer, filler, and other various components in the color forming layer used in the present invention are determined according to the required performance and recording suitability. Although not limited, usually 3 to 12 parts of an organic color developer, 3 to 12 parts of a sensitizer, per 1 part of the basic colorless dye (the following parts are parts by weight of the solid content), It is appropriate to use 1 to 20 parts of the filler and 10 to 25 parts of the binder based on the total solid content of the coloring layer.

The organic color developer, basic colorless dye, and sensitizer are each separated separately, or, if there is no problem, they are combined with other materials added as necessary, using a grinding machine such as a ball mill, attritor, or sand glider, or a suitable emulsifying device. The particles are atomized to a particle size of microns or less, and depending on the binder and purpose, the various quality control agents mentioned above are further added to form a coating liquid.

The coating liquid thus obtained is applied onto a substrate or an optical recording layer to form a thermosensitive coloring layer.

By laminating the thermosensitive coloring layer on the optical recording layer, the coloring of the optical recording layer is further hidden, resulting in an optical recording medium with a desirable appearance.

It is a preferred method to provide a protective layer on the surface of the thermosensitive coloring layer in order to reduce or prevent contamination from the external environment such as moisture, gas, water, solvents, oily substances, etc.

The protective layer must be transparent to visible light and have no adverse effect on the heat-sensitive color forming layer, and is formed by coating one or more binders selected from among the binders normally used for the heat-sensitive color forming layer. When a soluble near-infrared absorber is contained in this protective layer or between the protective layer and the thermosensitive coloring layer, the sensitivity of the -shoulder recording medium is increased.

Light sources necessary for optical recording include semiconductor laser diode bombing YAG laser, XE flash lamp,
0.7~ for quartz flash lamps, halogen lamps, etc.
Any light source that includes a wavelength in the near-infrared region of 2.5 μm can be used, and can be selected depending on the purpose of use.

(Function) As described above, a light absorbing layer containing a near-infrared absorber formed by mixing and heat-treating the thiourea derivative of the present invention and the metal compound of the present invention on a base material, and a basic colorless dye. An optical recording medium in which a thermosensitive color forming layer containing an organic color developer is laminated is recorded by irradiating a light source containing near-infrared light from above the recording medium.

The near-infrared absorber in the light absorption layer efficiently absorbs near-infrared light of any wavelength included in the irradiated light and converts it into heat. The generated heat quickly moves to the heat-sensitive coloring layer adjacent to the top or bottom of the light-absorbing layer, and there is enough heat to cause the basic colorless dye and organic color developer in the heat-sensitive coloring layer to react. A recorded image is created almost simultaneously with the light irradiation.

Furthermore, since the near-infrared absorber of the present invention has low absorption in the visible region, the background color of the light-absorbing layer is good, and in particular, when the light-absorbing layer is provided below the thermosensitive coloring layer, the background color is even better. Furthermore, since the near-infrared absorber and the thermosensitive coloring layer are separated, desensitization of the coloring layer does not occur.

(Example) Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples. Parts and percentages in the examples are by weight.

The optical recording papers of Examples and Comparative Examples below were evaluated based on optically recorded image density and background color. The measurements were carried out as follows, and the results are shown in Table 1.

Color density: Measure the image density with a Macbeth densitometer after irradiating with light.

Ground color: Measured on white paper using a Macbeth densitometer.

Examples 1 to 21 [Light Absorption Layer] The thiourea derivatives and metal compounds shown in Table 1 were separately prepared into the following compositions.

(A) Liquid thiourea derivative 50 parts 10% polyvinyl alcohol aqueous solution 25 parts Water 125 parts Total 200 parts (B)
Liquid metal compound 50 parts 10% polyvinyl alcohol aqueous solution 25 parts 125 parts 200 parts The multi-liquid having the above composition was wet-milled with an attritor until the average particle size was about 3 μm.

The fillers were dispersed according to the following formulations to obtain liquid (C).

(C) Liquid: Filler slurry silica 40 parts water
600 copies total
100 parts of liquid (C) is dispersed using a stirrer.

Liquid (A) (thiourea derivative dispersion) and liquid (B) (metal compound dispersion) were mixed so that the mixing ratio was as shown in Table 1, and then 250 parts of liquid (C) was added. , to a filling slurry containing 100 parts of a 10% polyvinyl alcohol aqueous solution, the number of parts of this mixed solution shown in the column of addition amount of near-infrared absorbing composition in Table 1 was added to form a light-absorbing layer coating solution. do.

This light-absorbing shoe coating liquid is applied onto high-quality paper with a basis weight of 60 g/rrr using a Meyer bar so that the coating amount is 5 g/rrf, and after drying, heat treatment is performed at 150°C to form a light-absorbing layer. Obtain a thermal conversion undersheet.

[Thermosensitive coloring layer] Liquid (E) (basic colorless dye dispersion) Basic colorless dye shown in Table 1 2.0 parts 10% polyvinyl alcohol aqueous solution 3.4 parts water
1,277 copies total
6.67 copies In addition, ODB, S-205, and 0DB-2 in the dye column of Table 1 have the following structure.

ODB: 3-diethylamino-6-methyl-7-anilinofluorane S-205: 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane 0DB-2 dibutylamino- 6-Methyl-7-anilinofluorane (F) liquid (color developer dispersion) Color developer shown in Table 1 6.0 parts P-benzylbiphenyl 4.0 parts 10% polyvinyl alcohol aqueous solution 12.5 Department water
2,5 Department total
25.0 Part list-
1, BPA, BPS, and POB in the color developer column are as follows.

BPA: Bisphenol A BPS: Bisphenol 5 POB: p-Hydroxybenzoic acid benzyl ester Solutions (E) and (F) were prepared by wet grinding each separately for 1 hour using a test sand glider according to the above formulation. .

Next, 6.67 parts of solution (E) (dye dispersion), 25 parts of solution (F) (developer dispersion), and hollow pigment (Lopeik 0P-48J manufactured by Rohm & Haas) with a concentration of 42.5% were dispersed. 11.76 parts of the liquid were mixed to prepare a heat-sensitive coloring layer coating liquid.

Apply the above coating liquid to the light-absorbing heat conversion undersheet in an amount of 3.
It was coated using a Meyer bar to give rJg/rrr and dried to obtain optical recording paper.

(Protective layer) 10% polyvinyl alcohol aqueous solution 100 parts Guoxal (40%) 5 parts total
105 parts The protective layer coating solution was coated on the optical recording paper using a Meyer bar in an amount of 2 g/rd and dried to obtain an optical recording paper with a protective layer.

Comparative example 1. 7. 8. 9 Add 10% to 250 parts of solution (C) used in Examples 1 to 21.
Filler slurry mixed with 100 parts of polyvinyl alcohol aqueous solution was coated on high-quality paper with a basis weight of 60 g/rrr using a Maya bar so that the coating amount was 5 g/rrf, dried, and then heat-treated at 150°C to infiltrate near-infrared rays. A comparative filler sheet containing no absorbent was obtained. Next, on this sheet, a paint containing the dye and developer shown in Table 1 in the same manner as in Examples 1 to 21 was applied using a Meyer bar at a coating amount of 3.0 g/rrr, dried, and compared. Example 1. 7. Recording sheets No. 8 and 9 were obtained.

Comparative example 2. 3. 4. 5. 6. 10 Table-1 Comparative Example 2. 3. The thiourea derivatives or metal compounds shown in rows 4 and 5 were added to solution (A) or (
B) Add and mix 20 parts of each to the filler slurry used in Comparative Example 1 to obtain an undercoating liquid, and apply this coating liquid to a high-quality paper with a basis weight of 60g/d using a Mayer bar so that the coating amount is 5g/ffl. After applying and drying, apply 15
The undersheets of Comparative Examples 2, 3.4, and 5 containing only one component of the near-infrared absorber were obtained by heat treatment at 0°C. On this sheet, a paint containing ODB and BPA as dyes and color developers in the same manner as in Examples 1 to 21 was applied at a rate of 3.0 g/ff.
Comparative Example 2. 3. Recording sheets Nos. 4 and 5 were obtained.

On the filler sheet obtained in Comparative Example 1, a thermosensitive coloring paint prepared in the same manner as in Examples 1 to 21 using ODB and BPA as dyes and color developers was added in the same manner as solution (A) in Examples 1 to 21. 20 parts of the 1-3-diphenylthiourea dispersion prepared above were mixed, coated, dried, and a heat-sensitive coloring layer was laminated to obtain a recording paper of Comparative Example 6.

On the thermosensitive coloring layer of the recording paper of Comparative Example 1, 20 parts of a 1-3-diphenylthiourea dispersion prepared in the same manner as the solution (A) of Examples 1 to 21 was added to the protective layer used in Examples 1 to 21. Coating liquid 10
A recording paper of Comparative Example 10 was obtained by applying and drying a mixture of 5 parts of the paint using a Meyer bar at a coating amount of 2.0 g/n.

Examples 1 to 21 and Comparative Examples 1 to 1 obtained as above
For optical recording of 0, camera strobe flash>ale
The light emitting window of 433D (manufactured by Sunpack Co., Ltd.) was narrowed down to 5%, and the coloring layer surface was irradiated to obtain an optical recording paper.

As is clear from Table 1, in the comparative examples that do not contain the near-infrared absorber of the present invention, or that consist of an under layer and a thermosensitive coloring layer that contain only one of a thiourea compound or a metal compound, no light irradiation occurs. No color develops. In contrast, the optical recording paper of the example in which a thermosensitive coloring layer was laminated on the light absorption layer containing the near-infrared absorber of the present invention obtained by mixing and heating a thiourea derivative and a metal compound had a high The image density and white background make it a practical optical recording paper.

In addition, when a protective layer is provided on the heat-sensitive coloring layer, both image density and background color are almost the same as when no protective layer is provided.
Furthermore, even if the surface of the optical recording paper is rubbed with a wet finger, the recording layer will not peel off, and it will be water resistant. Meter head LDC-
Laser light was irradiated using the device shown in Figure 1 using a condenser lens (MDPLAN 5.0.1” manufactured by Olympus Optical Co., Ltd.) and a condenser lens (MDPLAN 5.0.1” manufactured by Olympus Optical Co., Ltd.). The irradiation time was 11,500 seconds.The colored spots were measured using a densitometer (PDM manufactured by Roku Konishi Photo Industry Co., Ltd.).
-5), and the measured value was converted into a Macbeth density, and an extremely deep black colored image of 1.35 was obtained. On the other hand, when the optical recording papers of Comparative Examples 1 to 10 were irradiated with laser light under the same conditions, no recorded images were obtained. Then, irradiation was performed for an additional 10 minutes, but no color developed at all despite the extremely long irradiation time.

Example 23 The optical recording paper obtained in Example 1 was coated with a He-Ne laser head (Model 105-1, manufactured by Spectra-Physics, center wavelength 632.8n+s, output 5 mW) as a light source and a beam collimator (Japanese). Laser light was irradiated for 1 second to perform optical printing using the apparatus shown in FIG. 1 using a BC-5 manufactured by Kagaku Engineering Co., Ltd.

When the colored spots were measured using a densitometer (PDM-5' manufactured by Roku Konishi Photo Industry Co., Ltd.) and the measured values were converted into Macbeth density, a fully colored image of 1.33 was obtained. On the other hand, when the optical recording papers of Comparative Examples 1 to 10 were irradiated with laser light under the same conditions, no recorded images were obtained. Therefore, the same recording paper was subjected to long-term irradiation for 10 minutes, but no color developed at all.

(Effects of the Invention) As explained above, the optical recording medium of the present invention can directly obtain a high-resolution image by irradiation with near-infrared light from a semiconductor laser, a strobe flash, or the like. By using the near-infrared absorber of the present invention, which is composed of a less colored thiourea derivative and a metal compound, it can be used in a wide range of light sources such as semiconductor lasers with arbitrary near-infrared wavelengths and strobe flashes with continuous near-infrared wavelengths. This enabled the effective use of heat mode optical recording media, and brought good results to the practical application of heat mode optical recording media.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical recording device. 1... Laser light source, 2... Shutter, 3...
Condensing lens, 4... optical recording medium, 5... power source. Figure 1

Claims (5)

[Claims] (1) On the base material, there are general formulas (I), ▲mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1, R_2, R_3 are hydrogen, alkyl groups,
Represents a monovalent group selected from the group consisting of an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, and a 5- or 6-membered heterocyclic residue, R_1 and R_2 or R_2
and R_3 may be connected to form a ring. Each group may have one or more of amino groups, alkyl groups, alkenyl groups, aryl groups, aralkyl groups, nitro groups, halogen groups, hydroxyl groups, alkoxy groups, and acyl groups as substituents. ) and a thiourea derivative represented by the general formula (II) (R-X)_nM(II) (wherein R is hydrogen, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, and a heterocyclic residue (each group may have one or more substituents), and X is -C
OO, -SO_4, -SO_3, -PO_4, -O, n is an integer of 1 to 4) or chlorophyll M, M chlorophyllin sodium, bisacetylacetoate M (
M is a light-absorbing layer containing a near-infrared absorber formed by mixing and heat-treating a metal compound represented by a metal with an atomic weight of 40 or more excluding Groups IA and IIA of the periodic table, and a basic colorless dye. An optical recording medium characterized in that a thermosensitive color forming layer containing an organic color developer is laminated. (2) The optical recording medium according to claim 1, wherein the metal of the metal compound is copper and/or lead. (3) The optical recording medium according to claim 1 or 2, characterized in that a light absorption layer and a thermosensitive coloring layer are laminated in this order on the base material. (4) The optical recording medium according to claim 3, further comprising a transparent protective layer provided on the thermosensitive coloring layer. (5) The optical recording medium according to claim 1, 3 or 4, wherein the metal compound and the thiourea derivative are copper hydroxide and/or lead hydroxide and diphenylthiourea.